Scissortail Chromis, Chromis atrilobata

Scissortail Chromis, Chromis atrilobata. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, December 2010. Length: 8.9 cm (3.5 inches). Note that this fish lacks the prominent white spot at the rear base of the dorsal fin.

Scissortail Chromis, Chromis atrilobata. Fish caught from coastal waters off Puerto Los Cabos, Baja California Sur, October 2008. Length: 14.0 cm (5.5 inches). Provided via regurgitation by a 35 cm (14 inches) Flag Cabrilla.

Scissortail Chromis, Chromis atrilobata. Underwater photograph taken in coastal waters of the greater Los Cabos area, Baja California Sur, May 2018. Photograph courtesy of Bob Hillis, Ivins, Utah.

Scissortail Chromis, Chromis atrilobata. Underwater photographs taken in Zihuantanejo Bay, Guerrero, March 2018. Photographs courtesy of Ron Woheau, Zihuantanejo.

Scissortail Chromis, Chromis atrilobata. Underwater photograph taken in Zihuantanejo Bay, Guerrero, February 2020. Photograph and identification courtesy of Maude Jette, Dive Zihuantanejo, www.Divezihuatanejo.com.

Scissortail Chromis, Chromis atrilobata. Underwater photograph taken off Isle Coronado, Baja California Sur, May 2023. Photograph courtesy of Dr. Tom Bartol, Carlsbad, California.

The Scissortail Chromis, Chromis atrilobata, is a member of the Damselfish or Pomacentridae Family, and is known in Mexico as castañetas cola de tijera. Globally, there are eighty-four species in the genus Chromis, of which eight are found in Mexican waters, five in the Atlantic and three in the Pacific Ocean.

The Scissortail Chromis has a narrow oval fusiform compressed body that has a depth that is 36% to 40% of standard length, thus similar in nature to freshwater bluegills. They are metallic silvery gray in color with dark reddish brown tinges. Most fish have a prominent white spot just below the end of their dorsal fin base. Their caudal fin is deeply forked and each fin lobe is narrow and intensely black with sharp tips, thus resembling a pair of scissors (after which they are named). Their pectoral fin base is also very black. Their head has a small protrusible mouth that opens in the front with 2 rows of teeth. They have 2 anal spines and 10 to 12 rays, a single continuous dorsal fin with 12 spines and 12 or 13 rays, and 20 to 23 gill rakers on their lower arch. Their lateral line is incomplete and ends under the edge of their dorsal fin base. Their body is covered with large rough scales.

The Scissortail Chromis is a non-migratory species normally found in shallow water in large aggregations around rocky reefs, but they are also found at depths up to 79 m (260 feet). They reach a maximum of 13.4 cm (5.3 inches) in length. They are diurnal feeders consuming primarily algae, benthic invertebrates and plankton. Reproduction is oviparous with pairing of individuals; eggs are distributed demersal and adhere to the substrate due to their stickiness. The Scissortail Chromis  is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Scissortail Chromis is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from Guerrero Negro, Baja California, northward along the central and northwest coasts of Baja.

The Scissortail Chromis is very easy to identify, however, if confused it would be with the Silverstripe Chromis, Chromis alta (deep body lacking caudal fin sharp dark lobes; white spot at base of dorsal fin).

From a conservation perspective the Scissortail Chromis is currently considered to be of Least Concern with stable, widely distributed populations. They are small in stature and rare and of limited interest to most. They are classic nibblers, thus difficult to catch by hook and line.